It is commonly known to use various types of tower designs for i.a. modern wind power plants. Through the years, different variants have been applied, e.g. lattice work designs; however, in recent years the most preferred have particularly been steel towers made with tubular shape. These are typically made in lengths that allow handling on common roads and mainly with common transport means. When the tower elements reach the erection site, the tower is typically assembled of three or more tower segments, in some cases constituting an assembled tower of more than 100 metres or even over 150 metres.
Since nothing indicates that such towers for wind power plants will be smaller in the future, it is necessary with solutions that allow transport via the roads if not other and appreciably more expensive transport solutions are to be applied. It is thus a fact that the size of these towers is increasing, and that it is not uncommon for the towers to have such a large diameter that transporting via the road network is no longer possible without dividing the individual tower elements into lesser sections.
From WO 2004/083633 is known a solution where a tower element is divided into three sections longitudinally of the element. The individual sections are assembled by flanges at the long sides, constituting a traditional tower element when assembled. Such tower elements still require much workshop time for rolling and welding and are furthermore cumbersome to transport as yet.
Also, from WO 2005/075763 it is known to make towers for wind power plants in segments. These segments are assembled with traditional flange joints in the longitudinal direction of the segments and can be made with rectangular shape or with tapering shape. The horizontal joints between two adjoining segments are made without joining and are just sealed with a suitable sealing means. The reason for not joining the joints in horizontal direction mechanically is apparently due to the fact that on other prior art tower constructions there is the tradition that welded tower elements have a weakness in these joints. The joints are exposed to fatigue loads which in time cause rupture in the horizontal weld seams. In the solution described in WO 2005/075763, the individual segments are mounted displaced relative to the laterally arranged segment with an offset corresponding to between 50% and 75% of the length of the segment. The case is thus that the tower in principle is constructed of elements that are mounted with breaking joint or bond.
Towers made according to this principle have some drawbacks, however. For one thing, it is necessary with different lengths of segments in order to mount the segments with offset. Moreover, a tower element cannot be assembled on the ground which subsequently is hoisted in place on one or more already mounted tower sections, if the case is a conical tower as the joint faces are large in vertical direction. This process may, however, be performed more easily by making cylindric towers, but still with great difficulty.
An object of the invention includes a solution for a tower, preferably a tower for a wind power plant, where the tower is constructed of prefabricated segments, where production, transport and mounting of these segments can be effected in an easy way and where there is a large degree of flexibility in these steps.